Differential phase-contrast imaging is used, for example, to enhance the contrast of low absorbing specimen, compared to conventional amplitude contrast images. In EP 1 731 099 A1, an X-ray interferometer arrangement is described comprising a standard polychromatic X-ray source, a source grating, a beam splitter grating and an analyzer grating and an image detector. An object is arranged between the source grating and the beam splitter grating, i.e. the phase grating. By phase stepping the analyzer grating it is possible to record raw image data comprising phase information. The gratings, for example the phase grating and the analyzer grating, comprise a plurality of X-ray transparent slits between trenches of absorbing material, for example gold.